Defect inspection device and defect inspection method

ABSTRACT

To detect an infinitesimal defect, highly precisely measure the dimensions of the detect, a detect inspection device is configured to comprise: a irradiation unit which irradiate light in a linear region on a surface of a sample; a detection unit which detect light from the linear region; and a signal processing unit which processes a signal obtained by detecting light and detecting a defect. The detection unit includes: an optical assembly which diffuses the light from the sample in one direction and forms an image in a direction orthogonal to the one direction; and a detection assembly having an array sensor in which detection pixels are positioned two-dimensionally, which detects the light diffused in the one direction and imaged in the direction orthogonal to the one direction, adds output signals of each of the detection pixels aligned in the direction in which the light is diffused, and outputs same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/088,673,filed on Apr. 1, 2016, which is a continuation of application Ser. No.14/396,908, filed on Oct. 24, 2014, now U.S. Pat. No. 9,329,136, whichis a 371 National Stage of PCT/JP2013/062139, filed on Apr. 24, 2013,the disclosures of which are incorporated in their entirety herein byreference into this application. This application also claims priorityfrom Japanese Patent Application No. 2012-102819, filed on Apr. 27,2012, the disclosures of which are incorporated in their entirety hereinby reference into this application.

BACKGROUND

The present invention relates to a defect inspection method and a defectinspection device where an infinitesimal defect that exists on a surfaceof a sample is inspected, a position, a type and dimensions of thedefect are determined, and a result of the determination is output.

To maintain and enhance the yield of a product in a manufacturing linefor a semiconductor substrate, a thin film substrate and others, theinspection of a defect that exists on a surface of the semiconductorsubstrate, the thin film substrate and others is performed. For priorart for the defect inspection, technique disclosed in JapaneseUnexamined Patent Application Publication No. Hei 8-304050 (PatentLiterature 1), Japanese Unexamined Patent Application Publication No.2008-268140 (Patent Literature 2) and others is known.

In Patent Literature 1, it is described that detection sensitivity isenhanced by illuminating the same defect plural times in one inspectionby an illumination optical system that linearly illuminates and adetection optical system that divides and detects an illuminated regionon a line sensor and adding their scattered light.

In Patent Literature 2, it is described that 2n pieces of APDscorresponding to a laser beam band are linearly arrayed, appropriate twoof 2n pieces are combined, the difference between output signals of thetwo APDs in each combination is calculated, noise by reflected light iseliminated, and a defective pulse for scattered light is output.

CITATION LIST Patent Literature

Patent literature 1: Japanese Unexamined Patent Application PublicationNo. Hei 8-304050

Patent Literature 2: Japanese Unexamined Patent Application PublicationNo. 2008-268140

SUMMARY

For defect inspection used in a manufacturing process of a semiconductorproduct and others, it is demanded that an infinitesimal defect isdetected, the dimensions of the detected defect are precisely measured,a sample is inspected without destroying it (for example, withoutconverting the property of the sample), fixed inspection results aresubstantially acquired with regard to the number, positions, dimensionsand types of detected defects for example when the same sample isinspected and multiple samples are inspected within fixed time.

In the techniques disclosed in Patent Literature 1 and Patent Literature2, particularly as to an infinitesimal defect having the dimensions of20 nm or less for example, scattered light caused from the defect isextremely feeble and since a defect signal gets lost in noise byscattered light caused on a surface of a sample, noise from a detectoror noise form a detection circuit, the infinitesimal defect cannot bedetected. Or when power for illumination is increased to avoid thesituation, the temperature of the sample rises by illumination light andthe temperature damages the sample. Or when a scanning rate of thesample is reduced to avoid the situation, the area which can beinspected within fixed time of the sample or the number of samplesdecreases. It has been difficult to detect an infinitesimal defect athigh speed as described above.

For a method of detecting feeble light, a photon counting method isknown. Generally, a high-sensitivity, high-precision and stable signalis acquired by counting the number of detected photons for feeble lightbecause S-N ratio of the signal is enhanced. For one example of thephoton counting method, a method of counting the generated number ofpulsed current generated by the incidence of a photon on aphotomultiplier and an avalanche photodiode is known. However, sincefrequencies cannot be counted when plural photons are incident in shorttime and pulsed current is generated plural times because the speed of aresponse is slow, the quantity of light cannot be precisely measured andthe photon counting method cannot be applied to defect inspection.

Besides, for one example of another photon counting method, a method ofmeasuring the sum of pulsed current generated by the incidence of aphoton on each pixel by a detector configured by arraying multipleavalanche photodiode pixels is known. This detector is called a siliconphotomultiplier (Si-PM), a pixelated photon detector (PPD) or amulti-pixel photon counter (MPPC). According to this method, unlikephoton counting using the single photomultiplier and the avalanchephotodiode, since the speed of a response is fast, the quantity of lightcan be measured even if plural photons are incident in short time.However, since the detector in which multiple avalanche diodes arearrayed is operated as a detector having one “pixel”, this method cannotbe applied to high-speed or high-sensitivity defect inspection dependingupon the parallel detection of plural pixels.

To settle the abovementioned problems, in the present invention is adefect inspection method comprising: irradiating light in a linearregion on a surface of the sample; detecting light which is reflectedand scattered from the linear region on the sample where the light isirradiated; processing a signal acquired by detecting the reflected andscattered light; and detecting a defect on the sample on the basis ofthe result of the processing, wherein in step of detecting includes;diffusing the reflected and scattered light from the sample in onedirection and imaging the light in a direction perpendicular to the onedirection; detecting the reflected and scattered light diffused in onedirection and imaged in the direction perpendicular to the one directionby an array sensor on which detection pixels are arrangedtwo-dimensionally; adding an output signal from each detection pixelarranged in a direction in which the reflected and scattered light isdiffused out of output signals from the array sensor where the detectionpixels for detecting the reflected and scattered light are arrangedtwo-dimensionally; and sequentially extracting a signal acquired byadding the output signals from each detection pixel arranged in thedirection in which the reflected and scattered light is diffused in onedirection for imaging and processing the signals.

Besides, to achieve the abovementioned object, a defect inspectiondevice includes: irradiation unit which irradiates illumination light ona surface of a sample to be a linear region; detection unit whichdetects light which is reflected and scattered from the linear region onthe sample on which the light is irradiated by the irradiation unit; andsignal processing unit which processes a signal acquired by detectingthe reflected and scattered light and detects a defect on the sample,wherein the detection unit is provided with; an optical system thatdiffuses, in one direction, light which is reflected and scattered fromthe sample and images the light in a direction perpendicular to the onedirection; and a detection system that is provided with an array sensorwhere detection pixels are arrayed two-dimensionally, detects thereflected and scattered light diffused in one direction by the opticalsystem and imaged in the direction perpendicular to the one direction,and adds and outputs an output signal of each detection pixel arrangedin the direction in which the reflected and scattered light is diffused.

According to the present invention, the defect inspection device and theinspection method can be provided where the whole surface of the samplecan be scanned in a short time, an infinitesimal defect can be detected,reducing thermal damage to the sample, the dimensions of the detecteddefect can be precisely calculated and a stable result of the inspectioncan be output.

The problems, the configuration and the effect except the abovementionedones will be clarified by the description of the following embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram showing the whole schematic configuration ofa defect inspection device equivalent to a first embodiment of thepresent invention.

FIG. 1B is a block diagram showing the configuration of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 2 is a block diagram showing a first example of the configurationof a illumination unit for acquiring an illumination intensitydistribution pattern realized by the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 3 is a block diagram showing a second example of the configurationof the illumination unit for acquiring an illumination intensitydistribution pattern realized by the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 4 is a block diagram showing a third example of the configurationof the illumination unit for acquiring an illumination intensitydistribution pattern realized by the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 5 is a block diagram showing a fourth example of the configurationof the illumination unit for acquiring an illumination intensitydistribution pattern realized by the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 6 is a block diagram showing a fifth example of the configurationof the illumination unit for acquiring an illumination intensitydistribution pattern realized by the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 7 is a side view showing one example of an optical element withwhich an illumination intensity distribution controller of the defectinspection device equivalent to the first embodiment of the presentinvention is provided.

FIG. 8 is a block diagram showing one example of an embodiment of meansfor measuring a state of illumination light and adjustment means in theillumination unit of the defect inspection device equivalent to thefirst embodiment of the present invention.

FIG. 9 is a block diagram showing one example of means for reducingenergy per single pulse by the branching of an optical path and thesynthesis of optical paths in the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 10A is a graph showing relation between pulses of a laser beamirradiated on a surface of a sample when no optical path is branched andsynthesized in the illumination unit of the defect inspection deviceequivalent to the first embodiment of the present invention and energy.

FIG. 10B is a graph showing relation between pulses of a laser beamirradiated on the surface of the sample when an optical path is branchedand optical paths are synthesized in the illumination unit of the defectinspection device equivalent to the first embodiment of the presentinvention and energy.

FIG. 11 is a plan view showing a shape of an illuminated region on thesurface of the sample by the illumination unit of the defect inspectiondevice equivalent to the first embodiment of the present invention.

FIG. 12 is a plan view according to the present invention showing alocus of a light spot by the scanning of the surface of the sample bythe illumination unit of the defect inspection device equivalent to thefirst embodiment of the present invention.

FIG. 13 is a side view showing arrangement and detection directionsviewed from the side in a detection unit of the defect inspection deviceequivalent to the first embodiment of the present invention.

FIG. 14 is a plan view showing the arrangement and detection directionsof low-angle detectors of the defect inspection device equivalent to thefirst embodiment of the present invention.

FIG. 15 is a plan view showing the arrangement and detection directionsof high-angle detectors of the defect inspection device equivalent tothe first embodiment of the present invention.

FIG. 16 is a block diagram showing the configuration of each detector1021 s, 1021 s′ installed at a low angle, 102 hs, 102 hs′ installed at ahigh angle respectively having a detection azimuth of 90 degrees in thedefect inspection device equivalent to the first embodiment of thepresent invention.

FIG. 17 is a block diagram showing the configuration of each detector1021 f, 1021 f′ installed in front at a low angle, 1021 b, 1021 b′installed at the back at the low angle, 102 hf installed in front at ahigh angle, 102 hb installed at the back at the high angle in the defectinspection device equivalent to the first embodiment of the presentinvention.

FIG. 18 is a perspective view showing a first example of a detectionsystem provided with a plural-pixel sensor in the detection unit of thedefect inspection device equivalent to the first embodiment of thepresent invention.

FIG. 19 is a front view showing a first example of a sensor face of anarray sensor of the detection system provided with the plural-pixelsensor in the detection unit in the first embodiment of the presentinvention.

FIG. 20 is a circuit diagram showing an equivalent circuit of componentsof the array sensor in the first embodiment.

FIG. 21 is a block diagram showing one embodiment of a signal processingunit in the first embodiment of the present invention.

FIG. 22A is a side view showing the combination of the array sensor anda microlens array in the detection system provided with the plural-pixelsensor in the first embodiment of the present invention.

FIG. 22B is a side view showing the combination of an array sensor as asecond example according to the present invention and an optical fiberarray in the detection system provided with the plural-pixel sensor inthe first embodiment of the present invention.

FIG. 23A is a perspective view showing the configuration of a variation1 of the detection system provided with the plural-pixel sensor in thedetection unit of the defect inspection device equivalent to the firstembodiment of the present invention.

FIG. 23B is a perspective view showing the configuration of a variation2 of the detection system provided with the plural-pixel sensor in thedetection unit of the defect inspection device equivalent to the firstembodiment of the present invention.

FIG. 23C is a plan view showing the configuration of the variation 2 ofthe detection system provided with the plural-pixel sensor in thedetection unit of the defect inspection device equivalent to the firstembodiment of the present invention.

FIG. 23D is a perspective view showing the configuration of thevariation 2 of the detection system provided with the plural-pixelsensor in the detection unit of the defect inspection device equivalentto the first embodiment of the present invention and shows a secondexample of the plural-pixel sensor in the detection unit according tothe present invention.

FIG. 24A is a front view showing a variation 1 of a sensor face of thearray sensor in the detection system provided with the plural-pixelsensor in the detection unit in the first embodiment of the presentinvention.

FIG. 24B is a front view showing a variation 2 of the sensor face of thearray sensor in the detection system provided with the plural-pixelsensor in the detection unit in the first embodiment of the presentinvention.

FIG. 25A is a side view showing a state in which pads of the arraysensor in the detection system provided with the plural-pixel sensor inthe detection unit in the first embodiment of the present invention andwiring on a substrate are connected via wire bonding.

FIG. 25B is a sectional view showing a state in which pads of the arraysensor in the detection system provided with the plural-pixel sensor inthe detection unit in the first embodiment of the present invention andwiring on a substrate are connected via each through hole.

FIG. 26 is a front view showing a variation 3 showing the sensor face ofthe array sensor of the detection system provided with the plural-pixelsensor in the detection unit in the first embodiment of the presentinvention.

FIG. 27A is a perspective view showing a sample and objective lenses ofplural detection systems in a state in which the plural detectionsystems are arranged on a meridian of a celestial sphere in thedetection unit in the first embodiment of the present invention.

FIG. 27B is a perspective view showing the sample and objective lens ofplural detection systems in a state in which the plural detectionsystems are arranged on a meridian of a celestial sphere and in aposition in which forward scattered light is detected in the detectionunit in the first embodiment of the present invention.

FIG. 28A is a graph showing output waveforms from array sensors of thedetection systems arranged on the meridian of the celestial sphere inthe detection unit in the first embodiment of the present invention.

FIG. 28B is a graph showing a state in which output waveforms from arraysensors of the detection systems arranged on the meridian of thecelestial sphere and an output waveform from an array sensor thatdetects forward scattered light are overlapped in the detection unit inthe first embodiment of the present invention.

FIG. 29A is a graph showing output waveforms from the array sensors whena position of the same angle of rotation on a sample is detected by thedetection systems arranged on the meridian of the celestial sphere inthe detection unit in the first embodiment of the present invention in acase where the sample is spirally scanned by illumination light.

FIG. 29B is a graph showing that output waveforms from the array sensorswhen the position of the same angle of rotation on the sample isdetected by the detection systems arranged on the meridian of thecelestial sphere and an output waveform from the array sensor thatdetects forward scattered light are overlapped in the detection unit inthe first embodiment of the present invention in the case where thesample is spirally scanned by illumination light.

FIG. 30 is a block diagram showing the whole schematic configuration ofa defect inspection device equivalent to a second embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a defect inspection device that enablesenhancing defect defection sensitivity, enlarging a range of detectabledefects (a dynamic range) and detecting the defects at higher speed.Referring to the drawings, embodiments of the present invention will bedescribed below.

First Embodiment

FIG. 1A shows an example of the schematic configuration of a defectinspection device equivalent to this embodiment.

The defect inspection device is properly provided with a illuminationunit 101, a detection unit 102, a stage unit 103 on which a sample W canbe mounted, a signal processing unit 105, a control unit 53, a displayunit 54 and an input unit 55. The illumination unit 101 is properlyprovided with a laser source 2, an attenuator 3, an outgoing beamadjuster 4, a beam expander 5, a polarization controller 6 and anillumination intensity distribution controller 7.

A laser beam emitted from the laser source 2 is adjusted to desired beamintensity in the attenuator 3, the laser beam is adjusted in a desiredbeam direction and in a beam traveling direction in the outgoing beamadjuster 4, the laser beam is adjusted to a desired beam diameter in thebeam expander 5, the laser beam is adjusted to a desired polarized statein the polarization controller 6, the laser beam is adjusted to desiredintensity distribution in the illumination intensity distributioncontroller 7, and the laser beam is irradiated onto an inspection objectregion of a sample 1.

An angle of incidence (an angle of inclination to a normal of thesurface of the sample) of illumination light to the surface of thesample 1 is determined by positions and angles of reflecting mirrors 81,82 arranged on an optical path of the illumination unit 101. Theincidence angle of the illumination light is set to an angle suitablefor detecting an infinitesimal defect. The larger incidence angle issuitable for detecting infinitesimal defects because the larger theincidence angle of the illumination light is, that is, the smaller anelevation angle of the illumination light (an angle between the surfaceof the sample and an optical axis of the illumination light) is, theweaker scattered light from minute irregularities (called haze) of thesurface of the sample 1 to be noise is in relation to scattered lightfrom a minute foreign matter on the surface of the sample 1. Therefore,when scattered light from the minute irregularities of the surface ofthe sample 1 interferes with the detection of an infinitesimal defect,it is desirable that the incidence angle of the illumination light isset to 75 degrees or more (15 degrees or less in terms of the elevationangle).

In the meantime, when the shortage of the quantity of scattered lightfrom a defect interferes with the detection of the infinitesimal defect,it is desirable that the incidence angle of the illumination light isset between 60 degrees and 75 degrees (between 15 degrees and 30 degreesin terms of the elevation angle) because, in oblique incidentillumination, the smaller the incidence angle of the illumination lightis, the more the absolute quantity of scattered light from a minuteforeign matter is. Besides, in oblique incident illumination, scatteredlight from a defect on the surface of the sample 1 increases, comparedwith the other polarized light by turning the polarization ofillumination light p-polarized light by polarization control in thepolarization controller 6 of the illumination unit 101. Moreover, whenscattered light from minute irregularities of the surface of the sample1 interferes with the detection of an infinitesimal defect, scatteredlight from the minute irregularities of the surface of the sample 1decreases, compared with the other polarized light by turning thepolarization of illumination light s-polarized light.

In addition, if necessary, an optical path of illumination light ischanged by inserting a mirror 21 into an optical path shown in FIG. 1Aof the illumination unit 101 by driving means not shown, theillumination light is sequentially reflected on mirrors 212, 213, andthe illumination light is irradiated from a direction substantiallyperpendicular to the surface of the sample (vertical illumination). Atthis time, illumination intensity distribution on the surface of thesample 1 is controlled as in a case of oblique incident illumination byan illumination intensity distribution controller 7 v. To acquirescattered light from a concave defect (a flaw by polishing and a crystaldefect due to crystal materials) on the surface of the sample in obliqueincident illumination by inserting a beam splitter in the same positionas the mirror 21, vertical illumination in which illumination light isirradiated substantially perpendicularly to the surface of the sample 1is suitable. An illumination intensity distribution monitor 24 shown inFIG. 1A will be described in detail later.

For the laser source 2, the one that oscillates an ultraviolet or vacuumultraviolet laser beam having a short wavelength (355 nm or less) as awavelength difficult to penetrate the inside of the sample 1 and outputsthe laser beam of 2 W or more is used for detecting an infinitesimaldefect in the vicinity of the surface of the sample 1. A diameter of anoutgoing beam is approximately 1 mm. To detect a defect inside thesample 1, a laser source that oscillates a visible or infrared laserbeam as a wavelength easy to penetrate the inside of the sample 1 isused.

The attenuator 3 is properly provided with a first polarizing plate 31,a half-wave plate 32 rotatable around the optical axis of illuminationlight and a second polarizing plate 33 as shown in FIG. 1B. Lightincident on the attenuator 3 is converted to linearly polarized light bythe first polarizing plate 31, a direction of polarization is turned toan arbitrary direction according to an azimuth of a phase lag axis ofthe half-wave plate 32, and the light passes the second polarizing plate33. Optical intensity is extinguished at arbitrary ratio by controllingthe azimuth of the half-wave plate 32. When a degree of linearpolarization of light incident on the attenuator 3 is fully high, thefirst polarizing plate 31 is not necessarily required. For theattenuator 3, the one in which relation between an input signal and arate of extinction is calibrated beforehand is used. For the attenuator3, it is possible both to use an ND filter having gradated densitydistribution and to use plural ND filters having mutually differentdensity by switching.

The outgoing beam adjuster 4 is provided with plural reflecting mirrors41, 42. In this case, an embodiment when the outgoing beam adjuster isconfigured by the two reflecting mirrors 41, 42 will be described below.However, the present invention is not limited to this, and three or morereflecting mirrors may also be properly used. In this case, athree-dimensional rectangular coordinate system (XYZ coordinates) istemporarily defined and it is supposed that incident light on thereflecting mirror shall travel in a +X direction. The first reflectingmirror 41 is installed so that incident light is deflected in a +Ydirection (which means the incidence and reflection of light occurs inan XY plane) and the second reflecting mirror 42 is installed so thatthe light reflected on the first reflecting mirror 41 is deflected in a+Z direction (which means the incidence and reflection of light occursin a YZ plane). A position and a traveling direction (an angle) of lightoutgoing from the outgoing beam adjuster 4 are adjusted by the paralleldisplacement and the adjustment of a shift angle of each reflectingmirror 41, 42. The adjustment of a position and an angle on an XZ planeand the adjustment of a position and an angle on the YZ planerespectively of light (traveling in the +Z direction) outgoing from theoutgoing beam adjuster 4 can be independently performed by arranging sothat the incidence and reflection surface (the XY plane) of the firstreflecting mirror 41 and the incidence and reflection surface (the YZplane) of the second reflecting mirror 42 are perpendicular as describedabove.

The beam expander 5 is provided with two or more groups of lenses 51, 52and has a function to magnify a diameter of an incident parallel beam.For example, a Galilean beam expander provided with the combination of aconcave lens and a convex lens is used. The beam expander 5 is installedon a translational stage, not shown, having two axes or more and theadjustment of the position is possible so that a predetermined beamposition and the center are coincident. Besides, the beam expander 5 isprovided with a function to adjust a shift angle of the whole beamexpander 5 so that an optical axis of the beam expander 5 and apredetermined beam optical axis are coincident. The magnification of adiameter of a beam can be controlled by adjusting an interval betweenthe groups of lenses 51, 52 (a zoom mechanism). When light incident onthe beam expander 5 is not parallel, the magnification of the diameterof the beam and collimation (the semi-parallelization of a luminousflux) are simultaneously performed by adjusting the interval between thegroups of lenses 51, 52. A luminous flux may also be collimated byinstalling a collimator lens on the upstream side of the beam expander 5independently of the beam expander 5. The magnification of a beamdiameter by the beam expander 5 is approximately 5 to 10 times and abeam outgoing from the light source and having a diameter of 1 mm ismagnified to be approximately 5 to 10 mm.

The polarization controller 6 is configured by a half-wave plate 61 anda quarter-wave plate 62 and controls a polarized state of illuminationlight to be an arbitrary polarized state. On the way of the optical pathof the illumination unit 101, a state of light incident on the beamexpander 5 and a state of light incident on the illumination intensitydistribution controller 7 are measured by a beam monitor 22.

Reference numerals 22, 23 denote a beam monitor and the beam monitorsmonitor the intensity and a position of a laser beam on the opticalaxis.

FIGS. 2 to 6 schematically show positional relation between anillumination optical axis 120 led onto the sample surface by theillumination unit 101 and an illumination intensity distributionpattern. It should be noted, the configuration shown in FIGS. 2 to 6 ofthe illumination unit 101 shows apart of the configuration of theillumination unit 101, and the outgoing beam adjuster 4, a mirror 211,the beam monitors 22, 23 and others are omitted here.

FIG. 2 schematically shows the section of an incidence plane (a planeincluding the optical axis of illumination and the normal of the surfaceof the sample 1) of oblique incident illustration. Oblique incidentillumination tilts to the surface of the sample 1 on the incidenceplane. Substantially uniform illumination intensity distribution is madeon the incidence plane by the illumination unit 101. As shown in anillumination intensity distribution schematic diagram on the right sideof FIG. 2, the length of a part in which illumination intensity is evenin a linearly illuminated region is set to approximately 100 μm to 4 mmso as to inspect large area per unit time.

FIG. 3 schematically shows the section of a plane including the normalof the surface of the sample 1 and perpendicular to the incidence planeof the oblique incident illumination. On this plane, illuminationintensity distribution on the surface of the sample 1 is illuminationintensity distribution in which the intensity of the periphery isweaker, compared with that of the center. More concretely, theillumination intensity distribution is Gaussian distribution thatreflects the intensity distribution of light incident on theillumination intensity distribution controller 7, or a primary Besselfunction of the first kind that reflects a shape of an opening of theillumination intensity distribution controller 7 or intensitydistribution similar to sinc function. The length of illuminationintensity distribution (the length of a region having the illuminationintensity of the maximum illumination intensity of 13.5% or more) onthis plane is shorter than the length of the part in which illuminationintensity on the incidence plane is even and is set to approximately 2.5to 20 μm so as to reduce haze caused from the surface of the sample 1.The illumination intensity distribution controller 7 is provided withoptical elements including an aspherical lens, a diffractive opticalelement, a cylindrical lens array and a light pipe respectivelydescribed later. The optical elements that configure the illuminationintensity distribution controller 7 are installed perpendicularly to theillumination optical axis 120 as shown in FIGS. 2 and 3.

FIG. 4 shows a configuration in which the illumination intensitydistribution controller 7 is installed in parallel to the surface of thesample 1, compared with the configuration shown in FIG. 2. In this case,the illumination intensity distribution controller 7 is installed withthe controller tilted to the illumination optical axis 120.

Besides, each configuration shown in FIGS. 5 and 6 shows a configurationwhen the tilt to the surface of the sample 1 of the illumination opticalaxis 120 is changed in the configurations shown in FIGS. 3 and 2. Thatis, each configuration shown in FIGS. 5 and 6 shows a state when theorientation of the linearly illuminated region on the sample 1 to adirection in which the illumination optical axis 120 is incident on thesurface of the sample 1 is changed by 90 degrees with the casesdescribed in reference to FIGS. 2 and 3.

The configuration shown in FIG. 5 schematically shows the section of theincidence plane (the plane including the illumination optical axis andthe normal of the surface of the sample 1) of oblique incidentillumination and the oblique incident illumination is tilted to thesurface of the sample 1 on the incidence plane. On this plane,illumination intensity distribution on the surface of the sample 1 isillumination intensity distribution in which the intensity of theperiphery is weaker comparing to that of the center. In the meantime,the configuration shown in FIG. 6 schematically shows the section of aplane including the normal of the surface of the sample 1 andperpendicular to the incidence plane of oblique incident illumination.On the incidence plane, substantially uniform illumination intensitydistribution is formed.

The illumination intensity distribution controller 7 is provided withthe optical elements that act on the phase distribution and theintensity distribution of incident light. For the optical element thatconfigures the illumination intensity distribution controller 7, thediffractive optical element (DOE) 71 is used (see FIG. 7). Thediffractive optical element 71 is acquired by forming a minuteundulating shape having the similar dimension or smaller to/than awavelength of light on a surface of a substrate made of materials thattransmit incident light. For the material that transmits incident light,fused quartz is used in case an ultraviolet light is used for theillumination.

To inhibit the attenuation of light transmitted in the diffractiveoptical element 71, it is desirable to use a diffractive optical elementto which reflection reducing coating is applied. For the formation ofthe minute undulating shape, lithography process is applied.Illumination intensity distribution on the surface of the sampleaccording to the undulating shape of the diffractive optical element 71is formed by passing a quasi-parallel light, which is formed by thelight passing through the beam expander 5, through the diffractiveoptical element 71. The undulating shape of the diffractive opticalelement 71 is produced by designing to be a shape acquired based uponcalculation using Fourier optical theory so that illumination intensitydistribution formed on the surface of the sample has long evendistribution on the incidence plane.

The optical elements provided to the illumination intensity distributioncontroller 7 are provided with a translation adjustment mechanism havingtwo axes or more and a turn adjustment mechanism having two axes or moreso that a relative position and an angle with an optical axis ofincident light can be adjusted. Further, a focus adjustment mechanismbased upon a motion in a direction of the optical axis is provided. Foran alternative optical element having the similar function to thediffractive optical element 71, the combination of an aspherical lens, acylindrical lens array and a cylindrical lens and the combination of alight pipe and an imaging lens may also be used.

In the configuration shown in FIG. 1, a state of illumination light inthe illumination unit 101 is measured by the beam monitor 22. The beammonitor 22 measures a position and an angle (a traveling direction)respectively of illumination light that passes the outgoing beamadjuster 4 or a position and a wave front of illumination light incidenton the illumination intensity distribution controller 7 and outputsthem. The measurement of the position of illumination light is performedby measuring a position of the center of gravity of the opticalintensity of the illumination light. For a concrete position measurementmeans, a position sensitive detector (PSD) or an image sensor such as aCCD sensor and a CMOS sensor are used. The measurement of an angle ofillumination light is performed by the position sensitive detector orthe image sensor respectively which is installed in a position fartherfrom the light source than the position measurement means or installedin a position focused by a collimator lens. As shown in FIG. 8, aposition and an angle of illumination light measured by the beam monitor22 are input to the control unit 53 and are displayed on the displayunit 54. When the position or the angle of illumination light is off apredetermined position or angle, the outgoing beam adjuster 4 adjusts sothat the illumination light is returned to the predetermined position.

The measurement of a wave front of illumination light by the beammonitor 22 is performed to measure a degree of parallelization of lightincident on the illumination intensity distribution controller 7.Measurement by a shearing interferometer or measurement by a ShackHartman wave front sensor is performed.

The shearing interferometer measures a state of diverges or converges ofthe illumination light by observing a pattern of an interference fringeformed by projecting on a screen both of a reflected light from a frontsurface of an optical glass and a reflected light from a back surface ofthe optical glass. In the shearing interferometer, the optical glass isinserted by obliquely tilting in the optical path of illumination lightand it has the thickness of approximately several mm and both faces ofwhich are polished flatly. As the shearing interferometer, for anexample, SPUV-25 manufactured by SIGMA KOKI can be given. When an imagesensor such as a CCD sensor and a CMOS sensor is installed in a positionof the screen, the automatic measurement of the state in whichillumination light diverges or converges is possible.

The Shack Hartman wave front sensor divides a wave front by the minutelens array, projects the divided ones on an image sensor such as a CCDsensor, and measures the inclination of an individual wave front basedupon the displacement of a projected position. Compared with theshearing interferometer, detailed wave front measurement such as thepartial disturbance of a wave front is possible by using the ShackHartman wave front sensor.

When it is ascertained by the wave-front measurement that the lightincident on the illumination intensity controller 7 is not aquasi-parallel light but a divergence light or a convergence light, theincident light can be arranged to approach the quasi-parallel light bydisplacing the lens groups of the beam expander 5 which is installed onthe upstream side of the illumination intensity controller 7, in thedirection of the optical axis. Besides, when it is ascertained by thewave-front measurement that a wave front of the light incident on theillumination intensity controller 7 is partially tilted, the wave frontcan be adjusted to be approximately flat by inserting a spatial opticalphase modulation element (not shown) which is one type of a spatiallight modulator (SLM) on the upstream side of the illumination intensitycontroller 7 and applying suitable phase difference every position onthe section of a luminous flux so that the wave front is flat. That is,illumination light can be made to approximate quasi-parallel light. Thewave front precision (displacement from a predetermined wave front (adesigned value or an initial state)) of light incident on theillumination intensity distribution controller 7 is inhibited to be λ/10rms or less by the abovementioned wave front precisionmeasurement/adjustment means.

Illumination intensity distribution on the sample surface adjusted bythe illumination intensity distribution controller 7 is measured by theillumination intensity distribution monitor 24. As shown in FIG. 1, whenvertical illumination is used, illumination intensity distribution onthe sample surface adjusted by the illumination intensity distributioncontroller 7 v is also similarly measured by the illumination intensitydistribution monitor 24. The illumination intensity distribution monitor24 images the surface of the sample on an image sensor such as a CCDsensor or a CMOS sensor via lenses and detects as an image. An image ofillumination intensity distribution detected by the illuminationintensity distribution monitor 24 is processed in the control unit 53, aposition of the center of gravity of intensity, maximum intensity, amaximum intensity position, the width and the length (the width and thelength of an illumination intensity distribution region havingpredetermined radio or larger to predetermined intensity or more or amaximum intensity value) of the illumination intensity distribution andothers are calculated, and they are displayed together with a contour ofthe illumination intensity distribution and its sectional waveform onthe display unit 54.

In the case of oblique incident illumination, the disturbance ofillumination intensity distribution by the displacement of a position ofthe illumination intensity distribution and defocusing is caused by thedisplacement in height of the sample surface. To inhibit this, theheight of the sample surface is measured and when the height varies, thedisplacement is corrected by the illumination intensity distributioncontroller 7 or by the adjustment of height in the z-axis of the stageunit 103. The configuration for measuring the height of the samplesurface will be described below in reference to FIG. 8.

For the measurement of the height of the sample surface, the lightemitting portion 131 and the photodetector 132 that receives lightemitted from the light emitting portion 131 and reflected on the samplesurface are used. The light emitting portion 131 is provided with alight source such as a semiconductor laser and a projection lens. Thephotodetector 132 is provided with a light receiving lens and a positionsensitive detector. To measure a glossy surface of a sample such as asurface of semiconductor silicon or a surface of a magnetic disksubstrate, the light emitting portion 131 and the photodetector 132 arearranged so that light emitted from the light emitting portion 131 andregularly reflected on the sample surface is detected in thephotodetector 132. The displacement in height of the sample surface isdetected as the displacement of a position of a light spot detected bythe position sensitive detector in the photodetector 132 according to aprinciple of triangulation.

The correction of the displacement in an in-sample plane direction of anillumination light illuminated position due to the displacement inheight of the sample surface is performed by deflection angle adjustmentby a deflection means 80 installed on the downstream side of theillumination intensity distribution controller 7 to direct illuminationlight toward the sample surface. The deflection means 80 is providedwith a reflecting mirror 82 that deflects illumination light and apiezo-element 83 that controls a tilt angle to an illumination opticalaxis of the reflecting mirror, and controls the tilt angle at afrequency of 400 Hz or more so that the tilt angle is in a range ofapproximately ±1 m rad. The quantity of the displacement in thein-sample plane direction of the illumination light irradiated positionis acquired based upon a measured value of the displacement of theheight and an incidence angle of illumination light, and the reflectingmirror 82 is controlled by the deflection means 80 according to acontrol signal output from the control unit 53 to correct thedisplacement. The displacement in the in-sample plane direction of theillumination light irradiated position can also be measured by directlymeasuring a position of the center of gravity of illumination intensitydistribution and others using the illumination intensity distributionmonitor 24.

When the displacement in the in-sample plane direction of theillumination light irradiated position due to the displacement in heightof the sample surface is corrected by the deflection means 80, thedefocusing of the light spot is caused depending upon the quantity ofthe displacement because optical path length between the illuminationintensity distribution controller 7 and the surface of the sample 1varies from that before the correction. The variation of the opticalpath length is acquired based upon the measured value of thedisplacement of the height and the incidence angle of illumination lightand the defocusing is reduced by the adjustment of positions in thedirection of the optical axis of the optical elements provided to theillumination intensity distribution controller 7 or by the adjustment ofan angle of divergence by the beam expander 5 and others based upon thevariation of the optical path length.

When a pulse laser that can easily acquire high output is used for thelaser source 2, the energy of illumination applied to the sample 1concentrates in a moment in which a pulse laser is incident as shown inFIG. 10A thermal damage may be caused in the sample 1 due to themomentary rise of temperature by the incidence of the pulse laser. Toavoid this, it is effective to reduce energy per pulse, keeping totalenergy as shown in FIG. 10B by branching an optical path of the pulselaser and synthesizing the optical paths after optical path differenceis applied to the branched optical paths.

FIG. 9 shows one example of an optical system for embodying theabovementioned. Illumination light after passing through the beamexpander 5 is branched by the polarizing beam splitter 151 into a firstoptical path 1511 reflected by a polarizing beam splitter 151 and asecond optical path 1512 transmitted through the polarizing beamsplitter 151. The illumination light branched on the side of the firstoptical path 1511 is reflected by a retro-reflector 152, is returned onthe side of a polarizing beam splitter 153, and is reflected by thepolarizing beam splitter 153. The illumination light branched on theside of the first optical path travels on the same optical path as anoptical path of illumination light transmitted through the polarizingbeam splitter 151 and branched on the side of the second optical path1512. Then the branched two illumination lights are synthesized and thesynthesized illumination light is incident on the polarizationcontroller 6.

The retro-reflector 152 is provided with two or more reflecting mirrorsmutually perpendicular and backs input light in a direction reverse by180 degrees. The retro-reflector is also called a corner cube. In placeof the retro-reflector, independent two or more reflecting mirrors mayalso be used. To equalize the intensity of light reflected from thepolarizing beam splitter 151 and the intensity of light transmittedthrough it, the illumination light is adjusted to circularly polarizedlight or linearly polarized light polarized by 45 degrees obliquely andothers by a wave plate 150. When optical path difference between thefirst optical path 1511 and the second optical path 1512 is assumed L, atime interval Δtp between a pulse of light that passes the first opticalpath and a pulse of light that passes the second optical path is L/c.The momentary rise of temperature of the sample by a single pulse andthe rise of temperature due to the storage of heat by plural pulses areinhibited by setting the Δtp so that it is equal or longer to/than timerequired to soften the rise of temperature when the single pulse isincident.

A distributional pattern of illuminance (a light spot 20) formed on thesurface of the sample 1 by the illumination unit 101 and a samplescanning method will be described below in reference to FIGS. 11 and 12.For the sample W, a circular semiconductor silicon wafer is assumed. Thestage unit 103 is provided with a translational stage, a rotating stageand a Z stage for adjusting the height of the surface of the sample 1(all not shown). The light spot 20 has illumination intensitydistribution (linear illumination) long in one direction as describedabove, its longitudinal direction shall be S2, and a direction (adirection of the width of a line) substantially perpendicular to thelongitudinal direction S2 shall be S1. Scanning is performed in thecircumferential direction S1 of a circle having a rotation axis of therotating stage in the center by a rotational motion of the rotatingstage and in the translational direction S2 of the translational stageby a translational motion of the translational stage. The light spotdraws a spiral locus T on the sample 1 by scanning by distance equal toor shorter than the length in the longitudinal direction of the lightspot 20 in the scanning direction S2 while the sample is rotated once byscanning in the scanning direction S1, and the whole surface of thesample 1 is scanned.

Plural detection units 102 are arranged to detect scattered light inplural directions scattered from the light spot 20. Examples of thearrangement of the detection units 102 for the sample W and the lightspot 20 will be described in reference to FIGS. 13 to 15 below.

FIG. 13 is a side view showing the arrangement of the detection units102. An angle between the normal of the sample 1 and a detectiondirection (a central direction of an opening for detection) by thedetection unit 102 is defined as a detection zenithal angle. Thedetection unit 102 is configured by properly using a high-angle detector102 h with its detection zenithal angle of 45 degrees or less and alow-angle detector 1021 with its detection zenithal angle of 45 degreesor more. Plural high-angle detectors 102 h and plural low-angledetectors 1021 are provided so that scattered light scattered in manydirections is covered at each detection zenithal angle.

FIG. 14 is a plan view showing the arrangement of the low-angledetectors 1021. An angle between a traveling direction of obliqueincident illumination and the detection direction on a plane parallel tothe surface of the sample W is defined as a detection azimuth. Thelow-angle detector 1021 is properly provided with a low-angle frontdetector 1021 f, a low-angle side detector 1021 s, a low-angle backdetector 1021 b, and a low-angle front detector 1021 f′, a low-angleside detector 1021 s′ a low-angle back detector 1021 b′ which arerespectively located in symmetrical positions with former in relation toan illumination incidence plane. For example, the low-angle frontdetector 1021 f is installed so that its detection azimuth is between 0degree and 60 degrees, the low-angle side detector 1021 s is installedso that its detection azimuth is between 60 degrees and 120 degrees, andthe low-angle back detector 1021 b is installed so that its detectionazimuth is between 120 degrees and 180 degrees.

FIG. 15 is a plan view showing the arrangement of the high-angledetector 102 h. The high-angle detector 102 h is properly provided witha high-angle front detector 102 hf, a high-angle side detector 102 hs, ahigh-angle back detector 102 hb and a high-angle side detector 102 hs′located in a symmetrical position with the high-angle side detector 102hs in relation to the illumination incidence plane. For example, thehigh-angle front detector 102 hf is installed so that its detectionazimuth is between 0 degree and 45 degrees, the high-angle side detector102 hs is installed so that its detection azimuth is between 45 degreesand 135 degrees, and the high-angle back detector 102 hb is installed sothat its detection azimuth is between 135 degrees and 180 degrees. Acase where the four high-angle detectors 102 h are provided and the sixlow-angle detectors 1021 are provided is described above; however, thepresent invention is not limited to this case, and the number andpositions of the detectors may also be properly changed.

FIG. 16 shows an example of the concrete configuration of the detectionunit 102. Scattered light generated from the light spot 20 is convergedby an objective lens 201, then it is led to a detection system 204provided with a plural-pixel sensor by an imaging lens 203 after passingthrough a polarization filter 202, and an image of the scattered lightfrom the light spot 20 is detected by the detection system 204 providedwith the plural-pixel sensor having a configuration described later. Toefficiently detect the scattered light, it is desirable that thenumerical aperture (NA) for detection of the objective lens 201 is 0.3or more. In the case of the low-angle detector, a lower end of theobjective lens is cut if necessary so that the interference of the lowerend of the objective lens 201 with the sample W is avoided. Thepolarization filter 202 is configured by a polarizing plate or apolarizing beam splitter and is installed so that a linearly polarizedcomponent in an arbitrary direction is cut. For the polarizing plate, awire grating polarizing plate or a polarizing beam splitter thetransmittance of which is respectively 80% or more is used. When anarbitrary polarized component including elliptical polarization is cut,the polarization filter 202 configured by a wave plate and a polarizingplate is installed.

The detection unit 102 shown in FIG. 16 is an effective configuration inthe detectors 1021 s, 1021 s′, 102 hs and 102 hs′ respectively arrangedin a direction perpendicular to the longitudinal direction (the side) ofthe linear light spot 20 of the sample 1 shown in FIGS. 14 and 15.However, in the case of the detectors 1021 b, 1021 b′, 1021 f, 1021 f′,102 hf and 102 hb installed in oblique directions to the longitudinaldirection of the light spot 20, that is, in front of or at the back ofthe light spot 20, as distance from each position in the longitudinaldirection of the light spot 20 to the objective lens 201 is different,an image of scattered light from the light spot 20 cannot be formed inthe detection system 204.

Then, the configuration of the detection unit 102 in each detectorinstalled in the oblique direction to the longitudinal direction of thelight spot 20 of which an image of scattered light from the light spot20 can be formed in the detection system 204 will be described inreference to FIG. 17 below.

The configuration of the objective lens 201, the polarization filter 202and the imaging lens 203 in the configuration of the detection unit 102shown in FIG. 17 is the same as the configuration described in referenceto FIG. 16. In the detection unit 102 shown in FIG. 17, a diffractiongrating 206 and an imaging system 207 are provided at the back of theimaging lens 203 to enable forming an image of scattered light from thelight spot 20 in the detection system 204.

Scattered light generated from the light spot 20 is converged by theobjective lens 201 and after the converged scattered light passingthrough the polarization filter 202, an image (an intermediate image) ofthe sample surface is imaged on the diffraction grating 206 installed ona plane conjugate with the sample surface by the imaging lens 203. Theimage of the sample surface formed on the diffraction grating 206 isprojected and detected on light receiving surfaces of the plural-pixelsensor 204 by the imaging system 207. The plural-pixel sensor 204 isinstalled on the conjugate plane with the sample surface so that adirection of the array of pixels is coincident with a longitudinaldirection of an image of the light spot 20 in accordance with a shape ofthe light spot 20 long in one direction. The diffraction grating 206 isinstalled to diffract the light led by the imaging lens 203 for formingthe immediate image in the direction of the normal of the surface of thediffraction grating 206. And the shape of the grating of the diffractiongrating 206 is formed so that N“th” diffracted light of incident lightalong an optical axis of light led by the imaging lens 203 for formingthe intermediate image travels in a direction of a normal of a surfaceof the diffraction grating 206. To enhance diffraction efficiency, ablazed diffraction grating is used.

The displacement of a focus is also reduced in the direction S1 on thesample surface by adopting the abovementioned configuration andinstalling the plural-pixel sensor 204 on the conjugate plane with thesample surface, an effective field of view can be secured in a largerange, and scattered light can be detected with the reduced loss of thelight quantity.

FIG. 18 shows the configuration of the detection system 204 providedwith the plural-pixel sensor. An image of the sample surface is imagedon a conjugate plane 205 which is conjugate with the sample surface bythe objective lens 201 and the imaging lens 203 in the configurationshown in FIG. 16. The detection system 204 shown in FIG. 18 and providedwith the plural-pixel sensor is equipped with a slit plate 222, anuniaxial imaging system 223 and an array sensor 224. The slit plate 222is installed on the conjugate plane 205. A defect image 221 and anuniaxial enlarged image 225 of the defect image respectively in FIG. 18schematically show one example that a defect is located in the center ofa detection field of view of the detection unit 102. After the defectimage 221 is once imaged on the conjugate plane 205, the defect imagetravels in a direction of an optical axis of the detection unit 102 withan angle of divergence according to NA on the side of the image of theimaging lens 203. An image is formed from this light in a directioncorresponding to the scanning direction S2 on the conjugate plane 205 bythe uniaxial imaging system 223 and images on a light receiving surfaceof the array sensor 224. On the other hand, in a direction correspondingto the scanning direction S1 on the conjugate plane 205, the lightreaches the light receiving surface of the array sensor 224 in a statewith the angle of divergence.

The uniaxial imaging system 223 has a function that focuses light onlyin the direction corresponding to the scanning direction S1 and isconfigured by a cylindrical lens or the combination of the cylindricallens and a spherical lens. The defect image 221 is enlarged in thedirection corresponding to the scanning direction S1 by the action ofthe uniaxial imaging system 223. The size of the defect image on theconjugate plane 205 is determined by the optical resolution of thedetection unit 102 in the case that an infinitesimal detect is smallerthan a wavelength of illumination light, and concretely, the size isdetermined by the NA on the side of the image of the imaging lens 203(size of image of infinitesimal detect (spread of spotimage)=1.22×(wavelength)/(NA on image side)). The length in thedirection S1 of the uniaxial enlarged image 225 of the defect image,that is, magnification in the direction S1 is determined by optical pathlength between the conjugate plane 205 and the light receiving surfaceof the array sensor 224 and the NA on the side of the image of theimaging lens 203. The detection system 204 provided with theplural-pixel sensor is configured so that this length is substantiallyequal to the length in the direction S1 of the light receiving surfaceof the array sensor 224. The width in the direction S2 of the uniaxialenlarged image 225 of the defect image is determined by themagnification of the uniaxial imaging system 223. The detection system204 provided with the plural-pixel sensor is configured so that thislength is similar to the length in the direction S2 of the lightreceiving surface of the array sensor 224 or shorter.

Scattered light from the sample surface is produced from a position onwhich the light spot 20 is irradiated and is detected by the detectionunit 102. However, illumination light of relatively weak intensity alsosubstantially irradiates a region outside the light spot 20 by anundulation property of light. As a result, some of scattered lightproduced by a large foreign matter or at a corner of an end of thesample surface outside the light spot 20 is incident on the lightreceiving surface of the array sensor 224 and may deterioratesensitivity as noise. When this comes into question, this obstructivescattered light is excluded by installing the shielding slit plate 222and the noise is reduced. The shielding slit is provided with aslit-shaped opening (a light transmitted part) having width wider thanthe width of the image of the light spot 20 formed on the conjugateplane 205 and is installed so that the center of the slit-shaped openingis coincident with a position of the image of the light spot 20. As apart except the opening is shielded, scattered light from the partexcept a region in which the light spot 20 is located on the samplesurface is reduced.

FIG. 19 shows one example of the configuration of the light receivingsurface of the array sensor 224. The array sensor 224 has theconfiguration in which plural avalanche photodiodes (APD) are arrayedtwo-dimensionally. A light receiving part of the individual APD will becalled an APD pixel below. Voltage is applied to the APD pixel 231 sothat each is operated in Geiger mode (multiplication factor ofphotoelectron: 10⁵ or more). When one photon is incident on the APDpixel 231, a photoelectron is generated in the APD pixel 231 at aprobability according to the quantum efficiency of the APD pixel,photoelectrons are multiplied by the action of the Geiger-mode APD, anda pulsed electric signal is output. An APD pixel line 232 (a set of APDpixels encircled by a rectangular dotted line 232 shown in FIG. 19) in adirection shown by an arrow S1 is set as one unit, a pulsed electricsignal generated in each APD included in the pixel line is summed via awiring pattern 234 every APD pixel line in the direction S1, and thepulsed electric signals are output from a pad 235. Plural APD pixellines are arrayed in a direction shown by an arrow S2 and output signalsof APD pixels in each line are output in parallel.

FIG. 20 shows an example of a circuit diagram of a circuit equivalent toone APD pixel line 232 in the direction S1. One pair of a quenchingresistor 226 and APD 227 respectively shown in FIG. 20 corresponds toone APD pixel 231. A terminal 2351 is equivalent to the pad 235, aterminal 2352 is connected to each APD pixel, and reverse voltage V_(R)is applied. The APD 227 is operated in the Geiger mode by setting thereverse voltage V_(R) so that it is equal to or higher than thebreakdown voltage of the APD. Output electric signals (crest values ofvoltage and current or the quantity of charges) proportional to the sumof photons incident on the APD pixel line 232 in the direction S1 areacquired by adopting the configuration of the circuit shown in FIG. 20.Output electric signals (crest values of voltage and current or thequantity of charges) corresponding to each APD pixel line 232 in thedirection S1 are converted from analog to digital and are output inparallel as digital signals in time series.

Since the individual APD pixel outputs only the similar pulse signal tothat in a case where one photon is incident even if plural photons areincident in short time, total output signals in the PAD pixel line arenot proportional to the number of incident photons when the number ofphotons incident on the individual APD pixel per unit time increases,and the linearity of signals is impaired. Besides, when incident lightof fixed quantity (approximately mean one photon per one pixel) or moreis incident on all pixels in the APD pixel line, output signals aresaturated. The quantity of incident light per pixel can be reduced byadopting the configuration in which multiple APD pixels are arranged inthe S1 direction and the more precise count of photons is enabled. Forexample, when the quantum efficiency of the APD pixel is 30%, sufficientlinearity can be secured at optical intensity of approximately 1000photons or less per unit time of detection by setting the number ofpixels in the direction S1 to 1000, and optical intensity ofapproximately 3300 photons or less can be detected without beingsaturated.

To sense scattered light from the sample surface and detect from aninfinitesimal defect to a relatively large defect at a signal levelaccording to the dimensions, it is important to secure a dynamic rangeof the array sensor 224 that detects scattered light. To enlarge thedynamic range of the array sensor 224, the number of the APD pixels 231shown in FIG. 19 and arranged in the S1 direction has only to beincreased. However, when the total number of the APD pixel in the S1direction is simply increased, there occurs a problem that straycapacitance increases by extending the dimension in the S1 direction andthe operating speed is deteriorated, and also there occurs a problemthat the mounting space increases in mounting the array sensor 224.

As a way to cope this, a method of reducing the dimensions of the APDpixel 231 and increasing the number of the APD pixels 231 arranged inthe S1 direction without changing the whole length in the S1 directionis conceivable. However, when the whole dimensions of the APD pixel 231are reduced, the numerical aperture of each APD pixel 231 isdeteriorated, and the sensitivity of the array sensor 224 isdeteriorated.

Then, in this embodiment, as shown in FIG. 19, the dynamic range isenlarged without increasing stray capacity by reducing the dimension inthe direction S1 of the APD pixel 231 and increasing the number of theAPD pixels 231 arranged in the S1 direction without changing the wholelength in the S1 direction, the dimension in the S2 direction isincreased, and the numerical aperture is prevented from beingdeteriorated without changing the area of the individual APD pixel 231.Hereby, required detection sensitivity is secured without deterioratingthe operating speed even if the number of the APD pixels 231 arranged inthe S1 direction is increased, and the dynamic range can be enhanced.

In the configuration of the plural-pixel sensor 224 shown in FIG. 18,since means for equalizing optical intensity distribution in the S1direction is not particularly provided, the distribution of the quantityof light in the S1 direction of an optical image of a defect imaged onthe conjugate plane 205 is projected on the plural-pixel sensor 224 asit is. Reflected and scattered light from the sample are effected byGaussian distribution characteristic of the quantity of illuminationlight, their optical intensity is not even, and the optical intensity ofan end is weak, compared with the center arranged in the S1 direction ofthe plural-pixel sensor 224. This means that the number of the effectiveAPD pixels in the S1 direction decreases. The distribution in the S1direction of the uniaxial enlarged image 225 of the defect can be madeuniform by using, in place of the cylindrical lens, a lenticular lenswhere multiple minute cylindrical lenses having curvature in the S1direction are arranged in the S1 direction, a diffractive opticalelement or an aspherical lens. Hereby, a range of optical intensitywhere linearity can be secured or an unsaturated range of opticalintensity can be enlarged, keeping the number of the APD pixels in theS1 direction.

The number of photons at each position in the S2 direction on theconjugate plane 205 can be counted simultaneously and in parallel owingto the configuration of the abovementioned plural-pixel sensor 224.

Next, relation among the length of the light spot 20, the opticalmagnification of the detection unit 102 and the dimensions of thedetection system 204 provided with the plural-pixel sensor will bedescribed. When high-speed inspection is made at high sensitivity, thelength of the light spot 20 is set to approximately 500 μm. When thedetection system 204 provided with the plural-pixel sensor where 100pixels are arrayed at the pitch of 25 μm in the S2 direction (100 APDpixel lines 232 are arrayed in S1 the direction) is installed, theoptical magnification of the detection unit is 5 times and pitch betweenpixels projected on the sample surface is 5 μm.

When the sample is rotated at the rotating speed of 2000 rpm under theabove-described condition, the whole surface of a circular sample havingthe diameter of 300 mm is scanned in 9 seconds and the whole surface ofa circular sample having the diameter of 450 mm is scanned in 14seconds. In the case of higher-speed inspection, the length of the lightspot 20 is set to approximately 1000 μm. In this case, the opticalmagnification of the detection unit is 0.4 times and pitch betweenpixels projected on the sample surface is 62.5 μm. When the sample isrotated at the rotating speed of 2000 rpm on this condition, the wholesurface of the circular sample having the diameter of 300 mm is scannedin 5 seconds and the whole surface of the circular sample having thediameter of 450 mm is scanned in 7 seconds.

Next, the signal processing unit 105 that executes the classification ofvarious types of defects and the estimate of the dimensions of thedefects at high precision based upon scattered light intensity detectionsignals in various directions simultaneously detected by the pluraldetection optical systems that cover a wide angular range will bedescribed in reference to FIG. 21. In this case, to simplifydescription, the configuration in a case where two detection systems 102a, 102 b (not shown) in the detection unit 102 equipped with pluralsystems are provided of the signal processing unit 105 will be describedbelow. Each detection system 102 a, 102 b outputs a signal for each APDpixel line. But in this case, description in view of a signal in onepixel line of the signals will be made below, although it goes withoutsaying that the similar processing is also performed in parallel as tothe other pixel lines.

Output signals 500 a, 550 b corresponding to the detected quantity ofscattered light output from each detection elements provided to thedetection systems 102 a, 102 b are input to a digital processor 52 viaanalog processors 51 a, 51 b in which each band-pass filter is built. Inthe digital processor 52, defect signals 603 a, 603 b are extracted byhigh-pass filters 604 a, 604 b and are input to a defect determinationdevice 605. Since a defect is scanned in the S1 direction by the lightspot 20, a waveform of the defect signal is acquired by magnifying orreducing an illuminance distribution profile in the S1 direction of thelight spot 20. Accordingly, the SN ratio of the defect signals 603 a,603 b is improved by passing the waveform of each defect signal througheach high-pass filter 604 a, 604 b and cutting frequency bands includingrelatively much noise and a DC component. For each high-pass filter 604a, 604 b, a high-pass filter having a specific cut-off frequency anddesigned so that components that are equal to or exceed the frequencyare cut off or a band-pass filter or an FIR (Finite Impulse Response)filter similar to the waveform in which the shape of the light spot 20is reflected of the defect signal is used.

The defect determination device 605 applies a threshold process to theinput of the signal including the waveform of the defect output fromeach high-pass filter 604 a, 604 b and determines whether the defectexists or not. That is, since the defect signals based upon thedetection signals from the plural detection optical systems are input tothe defect determination device 605, the defect determination device 605can perform high-sensitivity defect inspection by applying the thresholdprocess to the sum of the plural defect signals and a weighted mean orORing and ANDing a group of defects extracted by the threshold processapplied to the plural defect signals on the same coordinates set on thesurface of the wafer, compared with the detection of a defect based upona single defect signal.

Further, the defect determination device 605 provides information ondefect, which is determined to exist, including defect coordinatesshowing a position of the defect on the wafer calculated based upon thewaveform of the defect and upon a sensitivity information signal andestimated values of the dimensions of the defect to the control unit 53as defect information, and outputs them to the display unit 54 andothers. The defect coordinates are calculated using the center ofgravity of the waveform of the defect for a criterion. The dimensions ofthe defect are calculated based upon an integrated value or the maximumvalue of the waveform of the defect.

Furthermore, each output signal from the analog processor 51 is input toeach low-pass filter 601 a, 601 b in addition to the high-pass filters604 a, 604 b that configure the digital processor 52, and a lowcomponent of a frequency corresponding to the quantity of scatteredlight (haze) from minute roughness in the light spot 20 on the wafer anda DC component are output from each low-pass filter 601 a, 601 b. Asdescribed above, the output from each low-pass filter 601 a, 601 b isinput to haze processing equipment 606 and there, the processing of hazeinformation is executed. That is, the haze processing equipment 606outputs a signal corresponding to a degree of haze every location on thewafer based upon the amplitude of an input signal acquired from eachlow-pass filter 601 a, 601 b as a haze signal. Besides, since theangular distribution of the quantity of scattered light from theroughness varies according to the spatial frequency distribution of theminute roughness, information of the spatial frequency distribution ofthe minute roughness can be acquired based upon the ratio in intensityof the haze signals and others from the haze processing equipment 606 byinputting the haze signal from each detector installed in mutuallydifferent azimuths and at different angles of the detection unit 102 tothe haze processing equipment 606 as shown in FIGS. 13 to 23.

An example of a variation of illumination intensity distribution made onthe sample surface by the illumination unit 101 will be described below.In place of the illumination intensity distribution (linearly) long inone direction and having substantially uniform intensity in thelongitudinal direction, illumination intensity distribution havingGaussian distribution in the longitudinal direction can also be used.Gaussian distribution illumination long in one direction is formed byproviding a spherical lens to the illumination intensity distributioncontroller 7, adopting a configuration in which an elliptic beam long inone direction is formed by the beam expander 5 or configuring theillumination intensity distribution controller 7 by plural lensesincluding a cylindrical lens.

Illumination intensity distribution long in one direction on the samplesurface and narrow in width in a direction perpendicular to thedirection is formed by installing a part or all of the spherical lensesor the cylindrical lenses respectively with which the illuminationintensity distribution controller 7 is provided in parallel to thesample surface. The abovementioned illumination intensity distributionhas characteristics that, compared with the case where uniformillumination intensity distribution is made, the variation ofillumination intensity distribution on the sample surface due to thevariation of a state of light incident on the illumination intensitydistribution controller 7 is small and the stability of the illuminationintensity distribution is high and, compared with a case where adiffraction optical element and a microlens array and others are used inthe illumination intensity distribution controller 7, the transmittanceof light is high and efficiency is satisfactory.

FIGS. 22A and 22B show the configuration of an example of a variation ofthe array sensor 224 shown in FIG. 18. As the area of a blind zonebetween APD pixels is relatively large, compared with the effective areaof a light receiving surface of an APD pixel 231 when the individual APDpixel 231 is small in an array sensor 224 in which the APD pixels arearrayed, the array sensor has a problem that the numerical aperture ofthe array sensor 224 is deteriorated and light detection efficiency isdeteriorated. Then, as shown in FIG. 22A, a rate of light incident onthe blind zone between the APD pixels 231 is reduced by installing amicrolens array 228 before the light receiving surface of the arraysensor 224 and an effective numerical aperture can be enhanced. Themicrolens array 228 is acquired by arranging minute convex lenses at thesame pitch as the array pitch of the APD pixels and is installed so thatlight (shown by a dotted line in FIG. 22A) parallel to a primary opticalaxis of incident light on the array sensor 224 is incident on thevicinity of the center of the corresponding APD pixel.

In the meantime, the configuration shown in FIG. 22B shows an example ofa case where in place of the microlens array 228 shown in FIG. 22A, anoptical fiber array 2290 is used.

FIG. 23A shows the configuration of the first variation of the detectionsystem 204 provided with the plural-pixel sensor. In this variation 1, adetection system 2041 provided with a plural-pixel sensor is providedwith an uniaxial imaging system 229 having imaging function in the S1direction and an uniaxial imaging system 223 having imaging function inthe S2 direction. A defect image 221 is enlarged in the S1 direction bymaking imaging magnification in the S1 direction by the uniaxial imagingsystem 229 higher than imaging magnification in the S2 direction by theuniaxial imaging system 223.

When a cylindrical lens is used for the uniaxial imaging system 229 andthe uniaxial imaging system 223, the magnification in the direction S1is higher than the magnification in the direction S2 by installing theuniaxial imaging system 229 closer to a conjugate plane 205 than theuniaxial imaging system 223 and making imaging relation in the S1direction. In the abovementioned configuration shown in FIG. 18, thereis a case where the optical intensity distribution in the S1 directionof the uniaxial enlarged image 225 or the dimension of a spread of theimage varies depending upon the angular distribution in the S1 directionof scattered light on the conjugate plane 205. In the meantime, in thisvariation, the size of an uniaxial enlarged image 2251 is determined bythe size of a defect image 221 and imaging magnification in the S1direction and in the S2 direction determined by the configurations andthe arrangement of the uniaxial imaging system 229 and the uniaxialimaging system 223. Since the size of the defect image 221 of aninfinitesimal defect is determined by the optical resolution of adetection unit 102 as described above, the size of the uniaxial enlargedimage 2251 hardly varies and a stable detection result is acquired.

For an array sensor 224, a photomultiplier tube having a high electronicmultiplication factor (10⁴ or more) can also be used in place of theavalanche photodiode. The use of the avalanche photodiode has anadvantage that the optical magnification of the detection unit 102 canbe reduced because the size of an individual pixel can be reduced andthe integration of several hundreds of or several thousands of pixels ormore is enabled at a low cost, while the photomultiplier tube has anadvantage that the dependency upon temperature of the multiplicationfactor of electrons is low and is stable.

FIG. 23B shows the configuration of a detection system 2042 as thesecond variation of the detection system 204 provided with theplural-pixel sensor. The detection system 2042 is provided with aplural-pixel sensor in which a condenser lens 300, a cylindrical fly-eyelens 301 and an imaging lens 302 that images in an uniaxial direction ofa direction S2 are used in place of the uniaxial imaging systems 229,223 described in reference to FIG. 23A.

In the variation 2, when light scattered from a defect image 221 on aconjugate plane 205 which is conjugate with a sample surface isconverged by the condenser lens 300 and is made incident on thecylindrical fly-eye lens 301, plural minute luminous fluxes divided in aS1 direction are outgoing from the cylindrical fly-eye lens 301 as shownin FIG. 23C. The plural minute luminous fluxes outgoing from thecylindrical fly-eye lens 301 are incident on the imaging lens 302 thatimages in an uniaxial direction by being respectively diffused as lightin which uniformity is enhanced in the S1 direction, are imaged in theS2 direction, and the plural minute luminous fluxes reach an arraysensor 224 as light uniformly distributed in the S1 direction.

Scattered light from a defect on the sample in which the uniformity inthe S1 direction is improved, compared with uniformity in theconfiguration in the variation 1 shown in FIG. 23A, can be detected bythe array sensor 224 by adopting such configuration. As a result, adynamic range of the array sensor 224 can be enlarged.

Further, FIG. 23D shows the third variation of the detection system 204provided with the plural-pixel sensor. In the configuration of adetection system 2043 provided with a plural-pixel sensor shown in FIG.23D, the microlens array described in reference to FIG. 22A is insertedbetween the cylindrical fly-eye lens 301 and the array sensor 224 in theconfiguration of the detection system 2042 provided with theplural-pixel sensor in the variation 2 shown in FIG. 23B. The effectiveaperture ratio of the array sensor 224 can be improved by adopting suchconfiguration, a dynamic range of the array sensor 224 is enlarged, anddetection sensitivity can be further improved.

FIG. 24A shows the first variation of the array sensor as aconfiguration for further improving the aperture ratio of the arraysensor 224 described in reference to FIG. 19.

In an array sensor 2241 shown in FIG. 24A, two APD pixel lines encircledby a dotted line 2321 are set as one unit by connecting APD pixels 2311,2331 having the similar shape to that of the array sensor 224 describedin FIG. 19. The APD pixels 2331 in the upper line and the APD pixels2311 in the lower line of the one unit 2321 of the array sensor 2241 areconnected to a common wiring pattern 2341. In this case, an uniaxialimaging system 223 or 302 is configured as shown in FIG. 23A or FIGS.23B and 23D so that an image of the scattered light from the defectprojected on the array sensor 2241 is imaged on the two APD pixel lines.

An apparent aperture ratio can be improved by configuring the sensorarray 2241 as described above, compared with the sensor array 224 shownin FIG. 19 though the resolution is deteriorated but detectionsensitivity can be improved.

Further, as the APD pixels 2311, 2331 arranged in the upper and lowertwo lines share the wiring pattern 2341, the number of wiring can bereduced and the array sensory 2241 can be miniaturized.

Further, stray capacity of the wiring is reduced by dividing the wiringpattern 2341 in two, providing electrode pads 236, 237 on both sides andreducing the substantial length of the wiring pattern and operatingspeed can be enhanced. In this case, signals from the electrode pads236, 237 are transmitted to wiring 240 formed on a substrate 241 viawire bonding 238, 239 shown in FIG. 25A. Or as shown in FIG. 25B,signals from electrode pads 236, 237 are input to wiring 244 formed onthe back of the array sensor 224 via through holes 242, 243 downwardpierced from the electrode pads 236, 237. A reference numeral 246denotes a through hole and the through hole is provided to connect thewiring 244 and an electrode (not shown) formed on a surface of the arraysensor 224. Any or all of the through holes 242, 243, 246 are formedaccording to the configuration of the array sensor 224.

FIG. 24B shows the second variation of the array sensor 224. In a sensorarray 2242 shown in this example, APD pixels 2311, 2331 arranged inupper and lower two lines, similar to those shown in FIG. 24A, are setas one unit 2322 of the APD pixels by connecting the pixels to a commonwiring pattern 2342. One end of the wiring pattern 2342 is connected toa transfer gate 2401. The transfer gate 2401 receives an enable signalsynchronized with the oscillation of a pulse laser emitted from thelaser source 2, synchronizes a detection signal output from the APDpixels in one unit 2322 with the oscillation of the pulse emitted fromthe pulse laser as the laser source 2, and inputs the detection signalto CCD 2402 for vertical transfer. The detection signal input to the CCDfor vertical transfer 2402 is transferred to CCD for horizontal transfer2403 at a predetermined line rate after the detection signal is storedby time for several pulses from the pulse laser. The detection signaltransferred to the CCD for horizontal transfer 2403 is seriallytransferred to a charge voltage conversion element 2404, is converted toa voltage signal in the charge voltage conversion element 2404, and isserially output.

By configuring the sensor array 2242 as described above, a signal outputfrom the charge voltage conversion element 2404 in the sensor array 2242can be processed as in a case where an output signal from aone-dimensional image sensor (a CCD sensor) is handled as a picturesignal.

Owing to the transfer gate 2401, noise caused by an after pulse and darkcurrent can be reduced by configuring as outputting a detection signalfrom one unit 2322 of the APD pixels in synchronous with the oscillationof the pulse from the pulse laser by receiving an enable signalsynchronized with the oscillation of a pulse laser emitted from thelaser source 2, inputting the output detection signal to the CCD forvertical transfer 2402, and storing the signal for several pulses.Hereby, a minute detection signal when feeble scattered light from aninfinitesimal defect is detected can be prevented from burying itselfunder noise and the detection sensitivity of the defect can be enhanced.

By configuring the sensor array 2242 as described above, circuitelements after the CCD for horizontal transfer 2403 are not required tobe configured by circuit elements having an operating characteristic ina high-frequency band close to 100 MHz and processing can be executed inparallel in multiple stages by increasing the number of units 2322 ofthe APD pixels arranged in a S2 direction. Hereby, a relatively largeregion can be collectively inspected by extending the dimensions in theS2 direction of a light spot on which illumination light 20 isirradiated on a sample using the sensor array 2242 including multipleunits 2322 of the APD pixels.

FIG. 26 shows an example of an array sensor 2243 in which the number ofAPD pixels included in a unit 2323 of APD pixels is further increased asthe third variation of the array sensor 224 shown in FIG. 19.

In the array sensor 2243 shown in FIG. 26, electrode pads 242, 243 areconfigured by respectively coupling the electrode pads 236, 237 of thearray sensor 2241 shown in FIG. 24A to upper or lower electrode pads.When the array sensor 2243 configured as described above is viewed as aone-dimensional image sensor in which plural pixels are arranged in a S2direction, a dynamic range of a signal equivalent to one pixel outputfrom the electrode pads 236, 237 can be further enlarged by increasingthe number of APD pixels connected to the electrode pads 236, 237respectively equivalent to one pixel of the one-dimensional image sensorthough resolution as the one-dimensional image sensor is deteriorated.

Hereby, a defect of size in a relatively large range from a furtherinfinitesimal defect in the order of a nanometer to a relatively largedefect of approximately several μm can be detected.

FIG. 27A schematically shows the arrangement of detection units 102having a different configuration from the configurations shown in FIGS.13 to 15. In FIG. 27A, the configuration in which a linear region 2705on a sample 1 is illuminated from an oblique direction shown by an arrow2700 based upon the sample 1 by the illumination unit 101 shown in FIG.1, the plural detection units 102 are arranged in a directionperpendicular to a longitudinal direction of the linear region 2705 (inpositions on a meridian 2710 of a celestial sphere from which the linearregion 2705 on the sample 1 is visible) is shown. The plural detectionunits 102 are respectively configured using the configuration of thedetection system 204 shown in any of FIGS. 18 to 26 in the opticalsystem shown in FIG. 16. In FIG. 27A, lenses 2011 to 2014 are equivalentto the objective lens 201 of the detection unit 102 shown in FIG. 16. Inthe following description, to simplify description, a case where theconfiguration shown in FIG. 18 is used for the detection system 204shown in FIG. 16 and the array sensor 224 having the configuration shownin FIG. 19 is used for the array sensor 224 shown in FIG. 18 will bedescribed. However, the configurations shown in FIGS. 22A to 26 can alsobe similarly applied.

An optical image of scattered light from a defect in each detection unit102 can be imaged on an APD pixel of an array sensor 224 by arrangingthe respective objective lenses 2011 to 2014 of the plural detectionunits 102 in a direction shown in FIG. 27A for the linear illuminatedregion 2705 on the sample 1 when the defect exists in the linearlyilluminated region 2705 on the sample 1. Therefore, scattered lightdescribed in reference to FIG. 18 relatively long in a S1 direction andimaged in a S2 direction can be detected.

When an optical image of scattered light from a defect is detected bythe array sensor 224 of each detection unit 102 arranged as describedabove in a case where the defect exists in the linear illuminated region2705 on the sample 1, a signal shown in FIG. 28A is respectively outputfrom the array sensor 224 of each detection unit 102. In FIG. 28A, awaveform 2801 represents a waveform of a signal output from the pad 235connected to the wiring pattern 234 connected to the APD pixel line 232of the array sensor 224 shown in FIG. 19. A waveform 2811 represents awaveform of a signal output from a pad 235 n shown in FIG. 19.

Since scattered light imaged in the direction S2 is detected on thearray sensor 224, no scattered light is detected in a region on the leftside of the waveform 2801 and in a region on the right side of thewaveform 2811 in FIG. 28A.

The configuration shown in FIG. 27B is acquired by adding a detectionunit that converges and detects forward scattered light from anilluminated region 2705 with a lens 2706 when illumination light isirradiated onto the linear illuminated region 2705 on a sample 1 from adirection shown by an arrow 2700 to the configuration shown in FIG. 27A.When the sample 1 is made of silicon (Si), the information of a defectis generally often included in the forward scattered light. Lenses 2011to 2014 are the same as those described in reference to FIG. 27A and areequivalent to the objective lens 201 of the detection unit 102.

Before the lens 2706 that converges the forward scattered light, amirror 2707 for intercepting regularly reflected light from the linearilluminated region 2705 on the sample 1 by illumination light irradiatedfrom the direction shown by the arrow 2700 is arranged so as to preventregularly reflected light from the linear illuminated region 2705 on thesample 1 from being incident on the lens 2706. An angle of the mirror2707 is set so that the regularly reflected light is not incident on anyof the lenses 2011 to 2014. In place of the mirror 2707, an interceptingpattern may also be arranged.

Waveforms of signals detected via the lenses 2011 to 2014 and outputfrom each array sensor 224 out of signals detected by each detectionunit 102 arranged as shown in FIG. 27B are the same as the signalwaveforms shown in FIG. 28A in the case shown in FIG. 27A. In themeantime, signal waveforms output from an array sensor 224 of thedetection unit 102 that detects the forward scattered light passedthrough the lens 2706 cannot be imaged in a S2 direction on the arraysensor 224 because the distances between each area in a longitudinaldirection of the linear illuminated region 2705 on the sample 1 and thelens 2706 are different and the forward scattered light passed throughthe lens 2706 diverges in the S2 direction, and a broad signal is outputfrom the array sensor 224.

FIG. 28B shows an example of a signal acquired by superimposing a signaldetected by the array sensor 224 through the lens 2012 and a signaldetected by the array sensor 224 through the lens 2706 for example inthe configuration shown in FIG. 27B. Signals 2801 to 2811 detectedthrough the lens 2012 have the same signal waveforms as those shown inFIG. 28A, while the signal detected through the lens 2706 has divergencein the S2 direction because the signal is not imaged in the S2 directionto be a broad signal shown by a broken light 2812.

FIG. 29A shows an example of output signal waveforms in the samerotation angle position when the sample is rotated three times whenillumination light is radially shifted and is spirally irradiated on thesample 1, rotating the sample as shown in FIG. 12. Scattered light froma position displaced radially (in a direction shown by an arrow R) bythe quantity of radial feed pitch is detected every rotation. In thisexample, the radial feed pitch every rotation of the sample 1 is madeshorter than the length in the S2 direction of the illuminated region2705 (20 in FIG. 11) so that the same location on the sample 1 isdetected plural times. Further, the radial feed pitch every rotation isset to displaced quantity by integral times of pitch between the APDpixel lines including the APD pixels 231 in the S2 direction when thesurface of the sample 1 is projected on the array sensor 224.

As shown in FIG. 19 for example, an image of scattered light from adefect is imaged between the APD pixel line 232 of the array sensor 224and the APD pixel line adjacent in the S2 direction at the time of firstrotation by setting the feed pitch of the illuminated region 2705 everyrotation of the sample 1 to the displaced quantity by integral times ofpitch in the S2 direction between the APD pixels 231 as described above,and even if no defect is detected in any pixel line, the image ofscattered light from the defect is imaged on some APD pixel line becausethe feed pitch of the illuminated region 2705 is not the integral timesof the APD pixel line in the S2 direction on the array sensor 224 whenthe sample 1 is rotated once. A contrary case is possible, however, inany case, possibility that a defect is overlooked can be reduced.

Besides, the detection of plural times of the same location on thesample 1 by spirally illuminating the sample 1 with illumination lightmeans that the same location on the sample 1 is detected in differentAPD pixel lines on the array sensor 224 and the effect that dispersionin detection sensitivity between the APD pixel lines can be equalized isalso obtained.

Generally, a peak position (a central position of a defect) can beacquired from an equalized waveform based upon the knowledge thatscattered light from the defect on a sample has Gaussian distribution,and the peak position can be detected at higher precision compared witha case of the feed pitch of integral times of a pixel.

FIG. 29B shows two signal waveforms in a state in which a signaldetected on the array sensor 224 through the lens 2012 for example and asignal detected on the array sensor 224 through the lens 2706 in theconfiguration shown in FIG. 27B when the sample 1 is spirallyilluminated in a rotated state are overlapped.

In this case, a peak position (a central position of a defect) can alsobe detected at higher precision based upon an equalized waveform bysetting to the similar feed pitch to that shown in FIG. 29A as describedin reference to FIG. 29A.

Moreover, in the case of a defect having a scattering characteristicthat forward scattered light is intense and upward and sideway scatteredlight is feeble, the possibility that the defect is overlooked can bereduced by using a signal acquired by detecting the forward scatteredlight on the array sensor 224 through the lens 2706, compared with acase where no detection signal based upon forward scattered light isused as shown in FIG. 29A. That is, the detection of more variousdefects is made possible by providing the optical system which detectsforward scattered light as shown in FIG. 27B.

Second Embodiment

Next, an example in which the detection unit 102 described in the firstembodiment is applied to an inspection device using a illumination unitdifferent from the illumination unit 101 shown in FIG. 1 will bedescribed in reference to FIG. 30.

FIG. 30 shows the inspection device provided with the illumination unit3100, the detection unit 3200 and lenses 3210, 3220. However, theinspection device is also provided with an optical system having thesimilar configuration to that of the detection unit 3200 at thesubsequence stage of each lens 3210, 3220. And the inspection device isprovided with a signal processing unit 3500, a control unit 3600, aninput unit 3700 and a display unit 3800 which are respectively similarto each unit shown in FIG. 1. In the inspection device shown in FIG. 30,an example in which the configuration in the second variation of thedetection system 204 shown in FIG. 23B provided with the plural-pixelsensor is adopted for the detection unit 3200 will be described below.However, in this embodiment, the configurations of the detection unit3200 and a detection system 204 provided with a plural-pixel sensorprovided at the subsequent stage of each lens 3210, 3220 are not limitedto the configuration described in reference to FIG. 23B and theconfigurations described in reference to FIGS. 18, 23A, 23D may also beadopted.

In the configuration shown in FIG. 30, the reference numeral 3101denotes an illumination light source and the illumination sourceoscillates an ultraviolet or vacuum ultraviolet laser beam having ashort wavelength (wavelength: 355 nm or shorter) as in the firstembodiment. The reference numeral 3102 denotes a polarizing plate andthe polarizing plate applies a desired polarization property to a laserbeam oscillated from the illumination light source 3101. The referencenumeral 3103 denotes a polarized beam splitter (PBS) and the polarizedbeam splitter selectively transmits the laser beam to which the desiredpolarization property is applied by the polarizing plate 3102. Thereference numeral 3104 denotes a birefringence prism. The birefringenceprism branches the laser beam transmitted in the PBS 3103 into twoluminous fluxes, and emits two beams. As for the laser beam branchedinto the two fluxes in the birefringence prism 3104, an oscillationdirection of polarized light is turned in the half-wave plate 3105, thepolarized light is turned circularly polarized light in the quarter-waveplate 3106, and transmitted through the objective lens 3107, and thecircularly polarized light simultaneously illuminates slightly distantregions 3001, 3002 on the surface of the sample 1.

Light incident on the objective lens 3107 of light reflected andscattered upward from the slightly distant regions 3001, 3002 on thesurface of the sample 1 on which the laser beam branched into the twofluxes are irradiated is transmitted in the quarter-wave plate 3106 tobe linearly polarized light, and after the linearly polarized light istransmitted through the half-wave plate 3105, it incidents on thebirefringence prism (Nomarski prism) 3106 and is synthesized to be oneluminous flux. The synthesized one luminous flux is incident on the PBS3103 and light having a specific polarized component (for example, ap-polarized component) of the reflected and scattered light from thesample 1 is reflected in a direction of the detection unit 3200 by thePBS 3103.

The light reflected in the direction of the detection unit 3200 isincident on an imaging lens 3201 and passes through a shielding slit3203 arranged on a conjugate plane 3202 (equivalent to the conjugateplane 205 which is conjugate with the surface of the sample in FIG. 23B)which is conjugate with the surface of the sample 1 for the objectivelens 3107 and the imaging lens 3201. The light that passes through theshielding slit 3203 is imaged on an array sensor 3207 in the S2direction by a condenser lens 3204, a cylindrical fly-eye lens 3205 andan uniaxial imaging system 3206 that converges in an uniaxial directionwhich are respectively configured like the optical system shown in FIG.23B, and the light is projected as light having width in the S1direction. The array sensor 3207 is the same as the array sensor 224described in reference to FIG. 23B.

When there is a slight difference in a level between the region 3001 andthe region 3002 on which the illumination light is respectivelyirradiated on the surface of the sample 1, a difference in optical pathlength occurs between light which is incident on and reflected from theregion 3001 and light which is incident on and reflected from the region3002. When the lights having the difference in optical path length asdescribed above are synthesized by the birefringence prism 3106,interference occurs. An image of reflected interferential light from thesample 1 is formed on the conjugate plane 3202, and the image isprojected on the array sensor 3207 by forming an image in the S2direction and a light having width in the S1 direction.

The minute difference in a level on the sample 1 can be detected byprocessing a signal telling the detection of the differentialinterference contrast image of the sample surface 1 projected on thearray sensor 3207.

In the meantime, scattered light in a direction of the objective lens3210 from the region 3001 and the region 3002 respectively illuminatedthrough the objective lens 3107 is converged by the objective lens 3210and is detected by a detection optical system 3211 arranged at thesubsequent stage of the objective lens 3210 and having the sameconfiguration as the detection unit 102 shown in FIG. 16. Since theconfiguration of the detection optical system 3211 is the same as thoseshown in FIGS. 16 and 23B, the description is omitted.

Similarly, the light scattered in a direction of the objective lens 3220from the region 3001 and the region 3002 respectively illuminatedthrough the objective lens 3107 is converged by the objective lens 3220,and is detected by a detection optical system 3221 installed at thesubsequent stage of the objective lens 3220 and having the sameconfiguration as the detection unit 102 shown in FIG. 16. Since theconfiguration of the detection optical system 3221 is the same as thoseshown in FIGS. 16 and 23B, the description is omitted.

A signal processing unit 3500 receives and processes the signal outputfrom the array sensor 3207 in the detection unit 3200, and detects theminute difference in a level on the sample 1. Besides, a detectionsignal of the scattered light detected by the detection optical system3211 through the objective lens 3210 and a detection signal of thescattered light detected by the detection optical system 3221 throughthe objective lens 3220 are both input to the signal processing unit3500, and processed there, and the defect on the sample 1 is detected.

On a display unit 3800, the minute difference in a level of the sample 1detected by the signal processing unit 3500 and the information of thedefect are displayed together with positional information on the wafer.

The present invention is not limited to the abovementioned embodimentsand includes various variations. For example, the abovementionedembodiments are detailed description for clarifying the presentinvention and the present invention is not necessarily limited to allthe described configurations. Besides, in place of a part of theconfiguration in the certain embodiment, the configuration in the otherembodiment can also be used and moreover, the configuration in the otherembodiment can also be added to the configuration in the certainembodiment. Further, another configuration can be added, deleted or usedto/from/in place of a part of the configuration of each embodiment.

LIST OF REFERENCE SIGNS

-   2: Laser source, 5: Beam expander, 6: Polarization controller, 7:    Illumination intensity distribution controller, 24: Illumination    intensity distribution monitor, 53: Control unit, 54: Display unit,    55: Input unit, 101: Illumination unit, 102: Detection unit, 103:    Stage unit, 105: Signal processing unit, 201: Objective lens, 202:    Polarization filter, 203: Imaging lens, 204: Detection system    provided with plural-pixel sensor, 224, 2241, 2242, 2243: Array    sensor.

The invention claimed is:
 1. A defect inspection method comprising: anirradiation light adjustment step in which light emitted from a lightsource is adjusted into a luminous flux with a quantity of light, aposition, a beam diameter and a polarization state; an irradiationintensity distribution control step in which the luminous flux obtainedby the irradiation light adjustment step is led to a surface of a samplewith an incident angle as required and an irradiation intensitydistribution is formed on a region on the surface of the samplespecified with an irradiation length longer in a first direction and anirradiation width shorter in a direction orthogonal to the firstdirection; a first sample scanning step in which the sample is displacedto a direction S1, at least in part, perpendicular to a longitudinaldirection of the irradiation intensity distribution according to theirradiation intensity distribution control step at an irradiationposition on the sample to which the irradiation light is irradiated; ascattered light detection step in which the scattered light obtainedinternally from a region on the sample irradiated by the irradiationlight through the irradiation intensity distribution control step at thefirst sample scanning step is imaged into a plurality of pixels andoutputs an arrayed scattered light detection signal; a second samplescanning step in which the sample is displaced by a distance smallerthan the irradiation length and a non-integer multiplication of a sizeof the plurality of pixels to a direction S2, at least in part, parallelto the longitudinal direction of the irradiation intensity distributionaccording to the irradiation intensity distribution control step at anirradiation position on the sample to which the irradiation light isirradiated each time the first sample scanning step is performed; and adefect determining step in which a plurality of arrayed scattered lightdetection signals outputted at different positions in the direction S2is averaged such that signals of different pixels corresponding topositions in proximity on the sample correspond to one another iscomputed to determine a presence of a defect on the sample.
 2. Thedefect inspection method according to claim 1, wherein the defectdetermining step comprises computing a peak position of the defect basedon the averaged signal, to output a position of the defect beingspecified so as to be outputted.
 3. A defect inspection devicecomprising: an irradiation means to adjust light emitted from a lightsource into a luminous flux with a quantity of light, a position, a beamdiameter and a polarization state to irradiate an irradiation light to alinear region on a surface of a sample; a shifting means to shift thesample to a longitudinal direction of the linear region to which theirradiation means irradiated the irradiation light as well as to adirection orthogonal to the longitudinal direction; a detecting means todetect a reflected and scattered light from the linear region on thesample to which the irradiation light is irradiated by the irradiationmeans by means of a plurality of pixels so as to detect all arrayedlight intensity distribution; a storing means to store informationaccording to the arrayed light intensity distribution detected by thedetecting means; and a signal processing means to detect a defect on thesample by processing a signal corresponding to the information accordingto the arrayed light intensity distribution stored in the storing means,wherein the signal processing means synthesize a signal intensity inwhich arrayed light intensity distributions obtained by the detectingmeans are averaged with a relative position between the irradiationmeans and the sample being shorter than a length of the linear regionand displaced by a distance of a non-integer multiplication of a size ofthe pixels to a longitudinal direction of the linear region, todetermine a presence of the defect.
 4. The defect inspection deviceaccording to claim 3, wherein the signal processing means computes acenter position of the defect based on the signal intensity in which thelight intensity distributions are averaged so as to output a defectposition.